i have a 94z28 A4 with bolt ons...the past few weeks of driving my car, randomly it just shuts off while driving whether it be at 5mph or at 70mph. the car doesnt misfire or anything, just dies suddenly. rpm's drop to "0" and check guages light comes on. ive had the car scanned for codes and nothing. now i have performed some tests as the car has died and it seems when it does it loses spark. sometimes for 2 seconds and sometimes i have to wait up to 15 min. the problem is also heat related because if i constantly keep my fans on(manual fan switch) it never dies, but if i turn car off for a little and fans go off whatever it is thats bad must heat soak and it dies shortly after i start driving it. and the weird part is car never dies wen in park....any suggestions? i was told ICM.

 

How old is the opti, when is the last time you installed cap,rotor,wires,and plugs?

 

Use a blow dryer to heat up one device at a time when the engine is completely cold. Heat it just the point it's too hot to touch and start the vehicle just long enough to see if it's causing your problem. Then move on to the next item.

Start with ICM, then coil, then OPTI. Highly unlikely the high voltage side of the opti is the problem. If the low voltage side were the problem, you would expect a code so that is highly unlikely as well.

 

A lot of guys spaced the ICM off the head a little bit with washers to let it get more air for cooling - if it turns out t be that...

 

Also, while it's running, try moving/shaking your wiring harness, connectors, battery to see if you can get it to stumble/die. I found a bad connection at my ICM that way several years ago. One of the female recepticles in the connector was making poor contact with the male pin in the ICM cavity. I took a sharp point of a wiring probe and pried the female recepticle sides inward just a tad and that effort fixed it. I'm not saying that is your problem but just offering this as a method to further isolate the issue. If nothing else, you can eliminate this as a potential cause. It is perplexing that you can prevent the issue by merely turning on the fans.

Things that I've encountered that caused my own z28 to spontaneously die...

• ICM connector - weak contact between one pin in harness and ICM.
• Burnt connector on ignition switch (the one under the dash on top of the steering column)
• Bad Alternator/weak battery.
• Crud on battery connector(under the red cap of the positive battery connector. Not visible to the eye until I pulled the connector off and looked). Every time I turned onto a roadway to the right (not left...weird), the motor would stumble and die. Sometimes it would restart, sometimes it wouldn't. It turned out that turning right allowed my battery to shift a bit and it would contort the battery connector and the car would die.
• The MAF connector pins would get a patina(oxidation film) and spontaneously die. If I popped the hood, got out of the car (sometimes embarrassingly at city intersections), disconnected and reconnected the connector 3 or 4 times to scuff off the patina, the car would start and I could drive it for a week or months before a reoccurrance. No electrical sprays I used made any difference. I replaced the MAF a few months ago and the error has not resurfaced since.

 

Also might try the Crankshaft position sensor. I had one that was bad. Car would randomly just shut down with no codes. Couldn't restart the car for 15-30 minutes later.

 

His 94 (OBD-I) does not have a crank position sensor. The CKP was added in 96 (OBD-II) for the purpose of misfire detection.

 

I did not know that. Good info to know!

 

Check your fuel pump, both for pressure and volume. As mine started to die, it had some weird symptoms, that I never connected to the pump until it died completely. Surging, hesitating, funny shifts, hard starting. Not all the time, but from time to time, I knew something was acting up, but didn't figure it out until after the fact.

 

Ignition switch on the column is a common thing to fail. I had to replace it on both of my cars. My blue car would shut off randomly just like a light switch, sometimes it would die for a split second and then fire back up before fully shutting down. Our cars are almost 20 years old now and lots of wearable parts are past their shelf life.

 

Ignition switch, fuel pump and starter were all my issues. All got worse with time until they went out for good.